<!DOCTYPE html>
<html>
    <head>
        <title>蓝旭第三次作业</title>
    </head>
    <body>
        <h1>第三题</h1>
        <script>
            var r = new Number(3);
           function area(r){
                var a=Math.PI*r*r;
                return a;
           }
            var s=area(r);
           console.log(s);
           document.write(s);
        </script>
    </body>
</html>